IHSS

Prognosis

If the LV wall is > 30mm, the incidence of Sudden Cardiac Death is 2% per year. Diastolic dysfunction is more common than systolic outflow obstruction.

Medical Treatment

Consider treating with beta-blockers, calcium antagonists, or disopyramide (Class IA antiarrhythmic, i.e. sodium channel blocker) to reduce dynamic LVOT obstruction.

Intraoperative Considerations

Anesthetic goals should be to minimize sympathetic stimulation, expand intravascular volume, and minimize decreases in left ventricular afterload

Volatile anesthetics are ideal in that they decrease contractility (but also decrease afterload and lead to junctional rhythms – consider a TEE probe or PA catheter with pacing capabilities). However, the tendency of volatile agents to produce junctional rhythms (HOCM depends on atrial kick) mandates caution – consideration should be given to TEE with pacing or a pacing PA catheter

A common anesthetic regimen is to combine volatile anesthesia with opiates, and pancuronium is avoided. Hypotension is treated with phenylephrine, which increases afterload and decreases ejection fraction, as opposed to ephedrine, which has beta activity and can thus both reduce afterload and stimulate the myocardium

In patients with significant obstruction, some degree of myocardial depression is usually desirable and can be achieved by the use of volatile anesthetic agents

Beta-blockers are also useful in counteracting the effects of sympathetic activation and decreasing obstruction. Phenylephrine may be an ideal vasopressor in these patients because it increases SVR (afterload) without augmenting contractility

Regional anesthesia may exacerbate left ventricular outflow obstruction by decreasing both cardiac preload and afterload

Interventional Treatment

Intracardiac defibrillator (AICD) can be lifesaving. Alcohol ablation of the septum is a non-operative treatment, and septal myomectomy and/or mitral valve replacement (eliminates anterior movement of ant. leaflet) are surgical options.